This invention relates to swirl tube apparatus for separating gas or isotope mixtures having at least one inlet port through which the gas enters tangentially into a chamber enclosed by a swirl tube.
In the swirl tube process of separation a gas jet is introduced tangentially into a stationary or rotating tube. Rotation of the gas causes the heavy particles to be separated from the lighter particles as a result of the centrifugal pressure field aided by the potential swirl effect.
A swirl tube arrangement of this type has been contemplated which at its major-diameter end is closed off by a wall. At this end, inlet ports directed tangentially to the end wall of the swirl tube are provided for introducing the gas mixture. Owing to the circular cross section of the chamber the gas is caused to rotate and is carried helically towards the minor-diameter end of the chamber. At this end the heavy gas fraction is extracted, while the lighter gas fraction rotating in predominantly inner areas flows back axially and is exhausted by an extraction pipe carried through the end wall of the swirl chamber.
This previously contemplated swirl tube apparatus provides a disadvantage, however, in that it exhibits relatively high friction losses making for poor separating output despite the higher gas velocities.
In a broad aspect the present invention provides a swirl tube arrangement of the noted type which is easy to manufacture and which gives a maximum of efficiency.
It is a particular object of preferred embodiments of the present invention to provide arrangements where the gas is fed in the longitudinally central area of the swirl tube and where the swirl tube has two axially adjacent swirl chambers of relative symmetrical arrangement. This type of construction eliminates the need for the respective end of the swirl tube, which not only reduces the wall friction but also combats the formation of turbulent flow in this area. The swirl tube apparatus of the present invention provides an advantage also in that the gas throughput is raised and the output of the device is doubled without appreciable added complexity of design.
When fed, the process gas flows into the separating area of the two swirl chambers and splits into two opposite symmetrical streams exhibiting a separating layer only in the wall area of the chamber.
The swirl chambers are given a conical shape in especially preferred practical embodiments of the invention, so that the reduction in diameter in the direction of flow increases the angular momentum over that of a cylindrical arrangement and that the reduction in gas velocity caused by wall friction is compensated at least in part.
The heavy fraction concentrating in the outer area of the swirl chamber is preferably extracted at the respective ends of the swirl chamber or swirl tube, while the lighter fraction is deflected in the center line area of the chambers and is there exhausted to ensure maximally defined separation of the two extraction points. In a further aspect of certain preferred embodiments of the present invention, deflector rings are provided which preferably continue into a convergent duct serving the concommitant function of extracting the light gas fraction, which prevents the two gas fractions from remixing.
For feeding the gas, several inlet ports are preferably provided which in the plane of symmetry are equally spaced over the circumference of the swirl tube.
The swirl tube apparatus of the present invention is suitable especially for forming cascades where in a further aspect of the present invention several swirl tubes are connected in line, with each pair of adjacent swirl tubes being fitted with at least one common extraction system. According to certain preferred embodiments of the invention, several such rows of swirl tubes are then arranged in parallel in compact disposition in a casing and are connected to common inlet and outlet ducts.
It has been shown that effective separation of the two gas components is achieved in swirl chambers of diameters in the order of several millimeters, because when these diameters are exceeded, the mixed gas will migrate into the eye of the swirl fast enough to prevent separation of the fractions. In connection with these sizing aspects, then, the swirl tubes of a row are advantageously integrated in a common component and combined in a block of, e.g., aluminum having bores to accommodate the rows of swirl tubes and collector ducts running at right angles thereto, according to yet further contemplated preferred embodiments of the invention.
The configuration of rows of swirl tubes in accordance with the present invention provides another advantage in that it can readily be fitted with a rotating whirl chamber wall with no appreciable added complexity of construction compared with individual swirl tubes. It will be useful, in certain preferred embodiments, to employ gas bearing provisions for the purpose where, e.g., two or more radial bearing cushions and two axial bearings, depending on the size of cascade, are pressurized with gas taken from the process gas.
A simplified design may also be used for the drive, which would, e.g., be a gasdynamic arrangement again pressurized with feed gas in practicing the present invention in connection with rotatable swirl chambers or tubes.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.